Generally, infrared (IR) spectroscopy is based on molecular vibration and rotation modes, as well as combination and overtone bands. Because molar absorptivity in the near-infrared (NIR) region of the electromagnetic spectrum can be quite small, NIR radiation can typically penetrate quite far into a sample (e.g., as compared to mid-infrared (MIR) radiation). Thus, IR spectroscopy techniques, such as diffuse reflectance NIR spectroscopy, can be useful for probing bulk material. Further, NIR spectroscopy generally requires limited or no sample preparation. Near-infrared spectroscopy (NIRS) can be used in materials characterization and molecular analysis applications as diverse as pharmaceuticals, medical diagnostics, neurology, neuroimaging, neonatal research, urology, food and agrochemical quality control, combustion product analysis, sports medicine, sports science, sports training, ergonomics, rehabilitation, and so forth.
Raman spectroscopy, another form of vibrational spectroscopy, can be used to determine vibrational, rotational, and/or other vibrational modes of a sample and/or sample components. Generally, Raman spectroscopy uses inelastic scattering (e.g., Stokes and Anti-Stokes scattering) of monochromatic light, which can be furnished using, for instance, a laser in the visible, NIR, or ultraviolet range. The laser light interacts with a sample, which shifts the energy of photons scattered by the sample from the laser. The energy shift can provide information about vibrational modes of the molecules that constitute the sample. Frequencies of molecular vibrations are specific to the chemical bonds and symmetry of molecules; thus the vibrational spectrum can be used to identify a particular sample and/or sample components. With Raman spectroscopy, little or no sample preparation is required. Further, Raman spectra can be collected from small volume samples (e.g., measuring less than approximately one micrometer (1 μm) in diameter). Raman spectroscopy can also be used in diverse applications including pharmaceuticals, medicine, chemistry, physics, nanotechnology, and so forth.